Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$68.31	8.782%	$74.309	$74.31	$74.30	$74.30
Purchase #2	$30.78	5.815%	$32.5699	$32.57	$32.55	$32.60
Purchase #3	$31.50	3.235%	$32.519	$32.52	$32.50	$32.50
Purchase #4	$113.40	11.558%	$126.5068	$126.51	$126.50	$126.50
Purchase #5	$42.26	9.125%	$46.1162	$46.12	$46.10	$46.10
Purchase #6	$75.46	8.683%	$82.0122	$82.01	$82.00	$82.00
Purchase #7	$62.26	13.799%	$70.8513	$70.85	$70.85	$70.90
7 purchase totals =	$423.97		$464.8844	$464.89	$464.80	$464.90